The mass SMS collection programme, codenamed Dishfire, does not just trace the communications of suspected criminals and terrorists, rather anybody who sends text messages can potentially be a target for government snooping.

As a result, the NSA is able to analyse vast numbers of text messages to snoop on information including missed call alerts, user location as a result of travel alerts and financial information from bank messages and receipts of financial transactions.

Leaked documents reveal an NSA presentation from 2011 titled "SMS Text Messages: A Goldmine to Exploit" revealing that the practice of intercepting information from mobile phones was common practice until at least 2012.

Documents also suggest that while communications about US phone numbers were removed from NSA databases after they had been analysed, information about citizens in countries outside of America – including the UK – was stored and in some cases shared.

As a result, GCHQ agents were able to observe mobile communications of UK citizens, including information about what numbers they had been communicating with.

"In contrast to [most] GCHQ equivalents, Dishfire contains a large volume of unselected SMS traffic," said a GCHQ memo.

"This makes it particularly useful for the development of new targets, since it is possible to examine the content of messages sent months or even years before the target was known to be of interest."

Nonetheless, GCHQ says it operates in a proportionate manner and within legal boundaries.

"All of GCHQ's work is carried out in accordance with the strict legal and policy framework which ensures that our activities are authorised, necessary and proportionate and that there is rigorous oversight," the department said in a statement.

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